lintcode-medium-Maximal Square

Given a 2D binary matrix filled with 0's and 1's, find the largest square containing all 1's and return its area.

 

Example

For example, given the following matrix:

1 0 1 0 0
1 0 1 1 1
1 1 1 1 1
1 0 0 1 0

Return 4.

 

public class Solution {
    /**
     * @param matrix: a matrix of 0 and 1
     * @return: an integer
     */
    public int maxSquare(int[][] matrix) {
        // write your code here
        
        if(matrix == null || matrix.length == 0 || matrix[0] == null || matrix[0].length == 0)
            return 0;
        
        int m = matrix.length;
        int n = matrix[0].length;
        int max = 0;
        
        int[][] dp = new int[m][n];
        
        for(int i = 0; i < m; i++)
            dp[i][0] = matrix[i][0];
        for(int i = 0; i < n; i++)
            dp[0][i] = matrix[0][i];
        
        for(int i = 1; i < m; i++){
            for(int j = 1; j < n; j++){
                if(matrix[i][j] == 0){
                    dp[i][j] = 0;
                }
                else{
                     dp[i][j] = Math.min(dp[i - 1][j - 1], Math.min(dp[i - 1][j], dp[i][j - 1])) + 1;
                }
                
            }
        }
        
        for(int i = 0; i < m; i++)
            for(int j = 0; j < n; j++)
                if(dp[i][j] > max)
                    max = dp[i][j];
        
        return max * max;
    }
}